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In a store window, there was a box of berries having a total weight of 200 kg.
The berries were 98% water, by weight. After two days in the sun, the water content of the berries was only 90%, by weight.
What was the total weight of the berries after two days, in kg?
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I will assume that the weight of the box itself is irrelevant
and should not be considered.
Since the total weight of berries was initially 200 kg and 98% of the weight was water,
it means that the dry fiber was 200 - 0.98*200 = 200 - 196 = 4 kg.
After 2 days drying the berries in the sun, these 4 kg of dry fiber represent only 100% - 90% = 10% of the current total mass.
Hence, the current mass of the 90% wet berries after 2 days of drying in the sun is = 4*10 = 40 kg.
ANSWER. The current mass of the 90% wet berries after 2 days of drying in the sun is 40 kg.
Solved.
This problem is very SPECIAL, because at this point, after getting this unexpected answer,
a reader is expected to experience and to express the feeling of amazement, as if he or she sees some miracle.
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This time, when people measured weight in kilograms, was a thing of the past 60 years ago.
Now cultured and educated people say "4 kilograms of mass" instead of "4 kilograms of weight".